Global motion models for motion vector inter prediction

ABSTRACT

A decoder is configured to receive a bit stream including a current frame and a picture header associated with the entire current frame, determine, as a function of the picture header, that one global motion mode is enabled for the entire current frame, the enabled global motion mode being selected from a group including translational motion, 4-parameter affine motion, and 6-parameter affine motion, detect, based on the enabled global motion mode, a plurality of parameters applicable to the entire frame, and decode the current frame using the detected parameters.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Nonprovisional applicationSer. No. 17/006,633, filed on Aug. 28, 2020 and entitled “GLOBAL MOTIONMODELS FOR MOTION VECTOR INTER PREDICTION,” which is a continuation ofInternational Application No. PCT/US20/29931, filed on Apr. 24, 2020 andentitled “GLOBAL MOTION MODELS FOR MOTION VECTOR INTER PREDICTION,”which claims the benefit of priority of U.S. Provisional PatentApplication Ser. No. 62/838,528, filed on Apr. 25, 2019, and titled“GLOBAL MOTION MODELS FOR MOTION VECTOR INTER PREDICTION.” Each ofnonprovisional application Ser. No. 17/006,633, InternationalApplication No PCT/US20/29931 and U.S. Provisional Patent ApplicationSer. No. 62/838,528 is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of videocompression. In particular, the present invention is directed to globalmotion models for motion vector inter prediction.

BACKGROUND

A video codec can include an electronic circuit or software thatcompresses or decompresses digital video. It can convert uncompressedvideo to a compressed format or vice versa. In the context of videocompression, a device that compresses video (and/or performs somefunction thereof) can typically be called an encoder, and a device thatdecompresses video (and/or performs some function thereof) can be calleda decoder.

A format of the compressed data can conform to a standard videocompression specification. The compression can be lossy in that thecompressed video lacks some information present in the original video. Aconsequence of this can include that decompressed video can have lowerquality than the original uncompressed video because there isinsufficient information to accurately reconstruct the original video.

There can be complex relationships between the video quality, the amountof data used to represent the video (e.g., determined by the bit rate),the complexity of the encoding and decoding algorithms, sensitivity todata losses and errors, ease of editing, random access, end-to-end delay(e.g., latency), and the like.

Motion compensation can include an approach to predict a video frame ora portion thereof given a reference frame, such as previous and/orfuture frames, by accounting for motion of the camera and/or objects inthe video. It can be employed in the encoding and decoding of video datafor video compression, for example in the encoding and decoding usingthe Motion Picture Experts Group (MPEG)-2 (also referred to as advancedvideo coding (AVC) and H.264) standard. Motion compensation can describea picture in terms of the transformation of a reference picture to thecurrent picture. The reference picture can be previous in time whencompared to the current picture, from the future when compared to thecurrent picture. When images can be accurately synthesized frompreviously transmitted and/or stored images, compression efficiency canbe improved.

SUMMARY OF THE DISCLOSURE

In an aspect, a decoder is configured to receive a bit stream includinga current frame and a picture header associated with the entire currentframe, determine, as a function of the picture header, that one globalmotion mode is enabled for the entire current frame, the enabled globalmotion mode being selected from a group including translational motion,4-parameter affine motion, and 6-parameter affine motion, detect, basedon the enabled global motion mode, a plurality of parameters applicableto the entire frame, wherein if the enabled global motion mode istranslational motion detecting the plurality of parameters furthercomprises detecting, in the picture header, a x direction translationalmotion vector component and a y direction translational motion vectorcomponent and the x direction translational motion vector component andthe y direction translational motion vector component apply to theentire frame; if the enabled global motion mode is 4-parameter affinemotion, detecting the plurality of parameters further comprisesdetecting, in the picture header, four explicit affine motionparameters, the four explicit affine motion parameters apply to theentire frame; and if the enabled global motion mode is 6-parameteraffine motion, detecting the plurality of parameters further comprisesdetecting, in the picture header six explicit affine motion parametersand the six explicit affine motion parameters apply to the entire frame;and decode the current frame using the detected parameters.

In another aspect a method includes receiving, by a decoder, a bitstream including a current frame and a picture header associated withthe entire current frame, determining, by the decoder and as a functionof the picture header, that one global motion mode is enabled for theentire current frame, the enabled global motion mode being selected froma group including translational motion, 4-parameter affine motion, and6-parameter affine motion, detecting, by the decoder and based on theenabled global motion mode, a plurality of parameters applicable to theentire frame, wherein if the enabled global motion mode is translationalmotion detecting the plurality of parameters further comprisesdetecting, in the picture header, a x direction translational motionvector component and a y direction translational motion vector componentand the x direction translational motion vector component and the ydirection translational motion vector component apply to the entireframe; if the enabled global motion mode is 4-parameter affine motion,detecting the plurality of parameters further comprises detecting, inthe picture header, four explicit affine motion parameters and the fourexplicit affine motion parameters apply to the entire frame; and if theenabled global motion mode is 6-parameter affine motion detecting theplurality of parameters further comprises detecting, in the pictureheader six explicit affine motion parameters the six explicit affinemotion parameters apply to the entire frame; and decoding, by thedecoder, the current frame using the detected parameters.

These and other aspects and features of non-limiting embodiments of thepresent invention will become apparent to those skilled in the art uponreview of the following description of specific non-limiting embodimentsof the invention in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more embodiments of the invention. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a diagram illustrating motion vectors of an example frame withglobal and local motion;

FIG. 2 illustrates three example motion models that can be utilized forglobal motion including their index value (0, 1, or 2);

FIG. 3 is a process flow diagram according to some exampleimplementations of the current subject matter;

FIG. 4 is a system block diagram of an example decoder according to someexample implementations of the current subject matter;

FIG. 5 is a process flow diagram according to some exampleimplementations of the current subject matter;

FIG. 6 is a system block diagram of an example encoder according to someexample implementations of the current subject matter; and

FIG. 7 is a block diagram of a computing system that can be used toimplement any one or more of the methodologies disclosed herein and anyone or more portions thereof.

The drawings are not necessarily to scale and may be illustrated byphantom lines, diagrammatic representations and fragmentary views. Incertain instances, details that are not necessary for an understandingof the embodiments or that render other details difficult to perceivemay have been omitted.

DETAILED DESCRIPTION

“Global motion” in video refers to motion and/or a motion model commonto all pixels of a region, where a region may be a picture, a frame, orany portion of a picture or frame such as a block, CTU, or other subsetof contiguous pixels. Global motion may be caused by camera motion; forexample, camera panning and zooming creates motion in a frame that cantypically affect the entire frame. Motion present in portions of a videomay be referred to as local motion. Local motion may be caused by movingobjects in a scene, such as without limitation, an object moving fromleft to right in the scene. Videos may contain a combination of localand global motion. Some implementations of the current subject mattermay provide for efficient approaches to communicate global motion to adecoder and use of global motion vectors in improving compressionefficiency.

FIG. 1 is a diagram illustrating motion vectors of an example frame 100with global and local motion. Frame 100 includes a number of blocks ofpixels illustrated as squares, and their associated motion vectorsillustrated as arrows. Squares (e.g., blocks of pixels) with arrowspointing up and to the left indicate blocks with motion that can beconsidered to be global motion and squares with arrows pointing in otherdirections (indicated by 104) indicate blocks with local motion. In theillustrated example of FIG. 1, many of the blocks have same globalmotion. Signaling global motion in a header, such as a picture parameterset (PPS) or sequence parameter set (SPS), and using the signaled globalmotion may reduce motion vector information needed by blocks and mayresult in improved prediction. Although for illustrative purposesexamples described below refer to determination and/or application ofglobal or local motion vectors at a block level, global motion vectorsmay be determined and/or applied for any region of a frame and/orpicture, including regions made up of multiple blocks, regions boundedby any geometric form such as without limitation regions defined bygeometric and/or exponential coding in which one or more lines and/orcurves bounding the shape may be angled and/or curved, and/or anentirety of a frame and/or picture. Although signaling is describedherein as being performed at a frame level and/or in a header and/orparameter set of a frame, signaling may alternatively or additionally beperformed at a sub-picture level, where a sub-picture may include anyregion of a frame and/or picture as described above.

As an example, and with continued reference to FIG. 1, simpletranslational motion may be described using a motion vector (MV) withtwo components MVx, MVy that describe displacement of blocks and/orpixels in a current frame. More complex motion such as rotation,zooming, and warping may be described using affine motion vector, wherean “affine motion vector,” as used in this disclosure, is a vectordescribing a uniform displacement of a set of pixels or pointsrepresented in a video picture and/or picture, such as a set of pixelsillustrating an object moving across a view in a video without changingapparent shape during motion. Some approaches to video encoding and/ordecoding may use 4-parameter or 6-parameter affine models for motioncompensation in inter picture coding.

For example, a six parameter affine motion can be described as:

x^(′) = a x + b y + c y^(′) = d x + e y + f

And a four parameter affine motion can be described as:

x^(′) = ax + by + c y^(′) = −bx + ay + f

where (x,y) and (x′,y′) are pixel locations in current and referencepictures, respectively; a, b, c, d, e, and f are the parameters of theaffine motion model.

Still referring to FIG. 1, parameters used describe affine motion may besignaled to a decoder to apply affine motion compensation at thedecoder. In some approaches, motion parameters may be signaledexplicitly or by signaling translational control point motion vectors(CPMVs) and then deriving affine motion parameters from thetranslational control point motion vectors. Two control point motionvectors may be utilized to derive affine motion parameters for afour-parameter affine motion model and three control point translationalmotion vectors may be utilized to obtain parameters for a six-parametermotion model. Signaling affine motion parameters using control pointmotion vectors may allow use of efficient motion vector coding methodsto signal affine motion parameters.

In some implementations, and continuing to refer to FIG. 1, globalmotion signaling may be included in a header, such as the PPS or SPS.Global motion may vary from picture to picture. Motion vectors signaledin picture headers may describe motion relative to previously decodedframes. In some implementations, global motion may be translational oraffine. A motion model (e.g., number of parameters, whether the model isaffine, translational, or other) used may also be signaled in a pictureheader. FIG. 2 illustrates three example motion models 200 that may beutilized for global motion including their index value (0, 1, or 2).

Still referring to FIG. 2, PPSs may be used to signal parameters thatcan change between pictures of a sequence. Parameters that remain thesame for a sequence of pictures may be signaled in a sequence parameterset to reduce the size of PPS and reduce video bitrate. An examplepicture parameter set (PPS) is shown in table 1:

pic_parameter_set_rbsp( ) { Descriptor  pps_pic_parameter_set_id ue(v) pps_seq_parameter_set_id  u(4)  mixed_nalu_types_in_pic_flag  u(1) pic_width_in_luma_samples ue(v)  pic_height_in_luma_samples ue(v) pps_conformance_window_flag  u(1)  if( pps_conformance_window_flag ) {  pps_conf_win_left_offset ue(v)   pps_conf_win_right_offset ue(v)  pps_conf_win_top_offset ue(v)   pps_conf_win_bottom_offset ue(v)  } scaling_window_explicit_signalling_flag  u(1)  if(scaling_window_explicit_signalling_flag ) {   scaling_win_left_offsetue(v)   scaling_win_right_offset ue(v)   scaling_win_top_offset ue(v)  scaling_win_bottom_offset ue(v)  }  output_flag_present_flag  u(1) subpic_id_mapping_in_pps_flag  u(1)  if( subpic_id_mapping_in_pps_flag) {   pps_num_subpics_minus1 ue(v)   pps_subpic_id_len_minus1 ue(v)  for( i = 0; i <= pps_num_subpic_minus1; i++ )    pps_subpic_id[ i ] u(v)  }  no_pic_partition_flag  u(1)  if( !no_pic_partition_flag ) {  pps_log2_ctu_size_minus5  u(2)   num_exp_tile_columns_minus1 ue(v)  num_exp_tile_rows_minus1 ue(v)   for( i = 0; i <=num_exp_tile_columns_minus1; i++ )    tile_column_width_minus1[ i ]ue(v)   for( i = 0; i <= num_exp_tile_rows_minus1; i ++ )   tile_row_height_minus1[ i ] ue(v)   if( NumTilesInPic > 1 )   rect_slice_flag  u(1)   if( rect_slice_flag )   single_slice_per_subpic_flag  u(1)   if( rect_slice_flag &&!single_slice_per_subpic_flag ) {    num_slices_in_pic_minus1 ue(v)   if( num_slices_in_pic_minus1 > 0 )     tile_idx_delta_present_flag u(1)    for( i = 0; i < num_slices_in_pic_minus1; i++ ) {     if(NumTileColumns > 1 )      slice_width_in_tiles_minus1[ i ] ue(v)     if(NumTileRows > 1 && ( tile_idx_delta_present_flag | |      SliceTopLeftTileIdx[ i ] % NumTileColumns = =0 ) )     slice_height_in_tiles_minus1[ i ] ue(v)     if(slice_width_in_tiles_minus1[ i ] = = 0 &&      slice_height_in_tiles_minus1[ i ] = = 0 &&       RowHeight[SliceTopLeftTileIdx[ i ] / NumTileColumns ] > 1 ) {     num_exp_slices_in_tile[ i ] ue(v)      for( j = 0; j <num_exp_slices_in_tile[ i ]; j++ )      exp_slice_height_in_ctus_minus1[ i ][ j ] ue(v)      i +=NumSlicesInTile[ i ] − 1     }     if( tile_idx_delta_present_flag && i< num_slices_in_pic_minus1 )      tile_idx_delta[ i ] se(v)    }   }  loop_filter_across_tiles_enabled_flag  u(1)  loop_filter_across_slices_enabled_flag  u(1)  cabac_init_present_flag u(1)  for( i = 0; i < 2; i++ )   num_ref_idx_default_active_minus1[ i ]ue(v)  rpl1_idx_present_flag  u(1)  init_qp_minus26 se(v) cu_qp_delta_enabled_flag  u(1)  pps_chroma_tool_offsets_present_flag u(1)  if( pps_chroma_tool_offsets_present_flag ) {   pps_cb_qp_offsetse(v)   pps_cr_qp_offset se(v)   pps_joint_cbcr_qp_offset_present_flag u(1)   if( pps_joint_cbcr_qp_offset_present_flag )   pps_joint_cbcr_qp_offset_value se(v)  pps_slice_chroma_qp_offsets_present_flag  u(1)  pps_cu_chroma_qp_offset_list_enabled_flag  u(1)  }  if(pps_cu_chroma_qp_offset_list_enabled_flag ) {  chroma_qp_offset_list_len_minus1 ue(v)   for( i = 0; i <=chroma_qp_offset_list_len_minus1; i++ ) {    cb_qp_offset_list[ i ]se(v)    cr_qp_offset_list[ i ] se(v)    if(pps_joint_cbcr_qp_offset_present_flag )     joint_cbcr_qp_offset_list[ i] se(v)   }  }  pps_weighted_pred_flag  u(1)  pps_weighted_bipred_flag u(1)  deblocking_filter_control_present_flag  u(1)  if(deblocking_filter_control_present_flag ) {  deblocking_filter_override_enabled_flag  u(1)  pps_deblocking_filter_disabled_flag  u(1)   if(!pps_deblocking_filter_disabled_flag ) {    pps_beta_offset_div2 se(v)   pps_tc_offset_div2 se(v)    pps_cb_beta_offset_div2 se(v)   pps_cb_tc_offset_div2 se(v)    pps_cr_beta_offset_div2 se(v)   pps_cr_tc_offset_div2 se(v)   }  }  rpl_info_in_ph_flag  u(1)  if(deblocking_filter_override_enabled_flag )   dbf_info_in_ph_flag  u(1) sao_info_in_ph_flag  u(1)  alf_info_in_ph_flag  u(1)  if( (pps_weighted_pred_flag | | pps_weighted_bipred_flag ) &&rpl_info_in_ph_flag )   wp_info_in_ph_flag  u(1) qp_delta_info_in_ph_flag  u(1)  pps_ref_wraparound_enabled_flag  u(1) if( pps_ref_wraparound_enabled_flag )   pps_ref_wraparound_offset ue(v) picture_header_extension_present_flag  u(1) slice_header_extension_present_flag  u(1)  pps_extension_flag  u(1) if( pps_extension_flag )   while( more_rbsp_data( ) )   pps_extension_data_flag  u(1)  rbsp_trailing_bits( ) }

With continued reference to FIG. 2, Additional fields may be added to aPPS to signal global motion. In case of global motion, presence ofglobal motion parameters in a sequence of pictures may be signaled in anSPS; a PPS may reference the SPS by SPS ID. An SPS in some approaches todecoding may be modified to add a field to signal presence of globalmotion parameters in SPS. For example a one-bit field may be added to anSPS. As a non-limiting example, if global_motion_present bit is 1,global motion related parameters may be expected in a PPS; ifglobal_motion_present bit is 0, no global motion parameter relatedfields may be present in the PPS. For example, a PPS as shown above intable 1 may be extended to include a global_motion_present field, forexample, as shown in table 2:

sequence_parameter_set_rbsp( ) { Descriptorsps_sequence_parameter_set_id ue(v) . . . global_motion_present  u(1)rbsp_trailing_bits( ) }

Similarly, a PPS may include a pps_global_motion_parameters field for aframe, for example as shown in table 3:

pic_parameter_set_rbsp( ) { Descriptor pps_pic_parameter_set_id ue(v)pps_seq_parameter_set_id ue(v) . . . pps_global_motion_parameters ( )rbsp_trailing_bits( ) }

In more detail, a PPS can include fields to characterize global motionparameters using control point motion vectors, for example as shown intable 4:

pps_global_motion_parameters ( ) { Descriptor motion_model_used  u(2)mv0_x se(v) mv1_y se(v) if(motion_model_used == 1) { mv1_x se(v) mv1_yse(v) } if(motion_model_used == 2) { mv2_x se(v) mv2_y se(v) } }

As a further non-limiting example, Table 5 below may represent anexemplary SPS:

seq_parameter_set_rbsp( ) { Descriptor  sps_seq_parameter_set_id  u(4) sps_video_parameter_set_id  u(4)  sps_max_sublayers_minus1  u(3) sps_reserved_zero_4bits  u(4)  sps_ptl_dpb_hrd_params_present_flag u(1)  if( sps_ptl_dpb_hrd_params_present_flag )   profile_tier_level(1, sps_max_sublayers_minus1 )  gdr_enabled_flag  u(1)  chroma_format_idc u(2)  if( chroma_format_idc = = 3 )   separate_colour_plane_flag  u(1) res_change_in_clvs_allowed_flag  u(1)  pic_width_max_in_luma_samplesue(v)  pic_height_max_in_luma_samples ue(v)  sps_conformance_window_flag u(1)  if( sps_conformance_window_flag ) {   sps_conf_win_left_offsetue(v)   sps_conf_win_right_offset ue(v)   sps_conf_win_top_offset ue(v)  sps_conf_win_bottom_offset ue(v)  }  sps_log2_ctu_size_minus5  u(2) subpic_info_present_flag  u(1)  if( subpic_info_present_flag ) {  sps_num_subpics_minus1 ue(v)   sps_independent_subpics_flag  u(1)  for( i = 0; sps_num_subpics_minus1 > 0 && i <= sps_num_subpics_minus1;i++ ) {    if( i > 0 && pic_width_max_in_luma_samples > CtbSizeY )    subpic_ctu_top_left_x[ i ]  u(y)    if( i > 0 &&pic_height_max_in_luma_samples > CtbSizeY ) {     subpic_ctu_top_left_y[i ]  u(y)    if( i < sps_num_subpics_minus1 &&     pic_width_max_in_luma_samples > CtbSizeY )     subpic_width_minus1[i ]  u(y)    if( i < sps_num_subpics_minus1 &&     pic_height_max_in_luma_samples > CtbSizeY )    subpic_height_minus1[ i ]  u(y)    if( !sps_independent_subpics_flag) {     subpic_treated_as_pic_flag[ i ]  u(1)    loop_filter_across_subpic_enabled_flag[ i ]  u(1)    }   }  sps_subpic_id_len_minus1 ue(v)  subpic_id_mapping_explicitly_signalled_flag  u(1)   if(subpic_id_mapping_explicitly_signalled_flag ) {   subpic_id_mapping_in_sps_flag  u(1)    if(subpic_id_mapping_in_sps_flag)     for( i = 0; i <=sps_num_subpics_minus1; i++ )      sps_subpic_id[ i ]  u(v)   }  } bit_depth_minus8 ue(v)  sps_entropy_coding_sync_enabled_flag  u(1)  if(sps_entropy_coding_sync_enabled_flag)  sps_wpp_entry_point_offsets_present_flag  u(1)  sps_weighted_pred_flag u(1)  sps_weighted_bipred_flag  u(1)  log2_max_pic_order_cnt_lsb_minus4 u(4)  sps_poc_msb_flag  u(1)  if( sps_poc_msb_flag )  poc_msb_len_minus1 ue(v)  num_extra_ph_bits_bytes  u(2) extra_ph_bits_struct( num_extra_ph_bits_bytes ) num_extra_sh_bits_bytes  u(2)  extra_sh_bits_struct(num_extra_sh_bits_bytes )  if( sps_max_sublayers_minusl >0)  sps_sublayer_dpb_params_flag  u(1)  if(sps_ptl_dpb_hrd_params_present_flag)   dpb_parameters(sps_max_sublayers_minus 1, sps_sublayer_dpb_params_flag ) long_term_ref_pics_flag  u(1)  inter_layer_ref_pics_present_flag  u(1) sps_idr_rpl_present_flag  u(1)  rpl1_same_as_rp10_flag  u(1)  for( i =0; i < rpl1_same_as_rp10_flag? 1 : 2; i++ ) {  num_ref_pic_lists_in_sps[ i ] ue(v)   for( j = 0; j <num_ref_pic_lists_in_sps[ i ]; j++)    ref_pic_list_struct( i, j )  } if( ChromaArrayType != 0 )   qtbtt_dual_tree_intra_flag  u(1) log2_min_luma_coding_block_size_minus2 ue(v) partition_constraints_override_enabled_flag  u(1) sps_log2_diff_min_qt_min_cb_intra_slice_luma ue(v) sps_max_mtt_hierarchy_depth_intra_slice_luma ue(v)  if(sps_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {  sps_log2_diff_max_bt_min_qt_intra_slice_luma ue(v)  sps_log2_diff_max_tt_min_qt_intra_slice_luma ue(v)  } sps_log2_diff_min_qt_min_cb_inter_slice ue(v) sps_max_mtt_hierarchy_depth_inter_slice ue(v)  if(sps_max_mtt_hierarchy_depth_inter_slice != 0 ) {  sps_log2_diff_max_bt_min_qt_inter_slice ue(v)  sps_log2_diff_max_tt_min_qt_inter_slice ue(v)  }  if(qtbtt_dual_tree_intra_flag ) {  sps_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v)  sps_max_mtt_hierarchy_depth_intra_slice_chroma ue(v)   if(sps_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {   sps_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v)   sps_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v)   }  } sps_max_luma_transform_size_64_flag  u(1)  if( ChromaArrayType != 0 ) {  sps_joint_cbcr_enabled_flag  u(1)   same_qp_table_for_chroma  u(1)  numQpTables = same_qp_table_for_chroma ? 1 : (sps_joint_cbcr_enabled_flag ? 3 : 2 )   for( i = 0; i < numQpTables; i++) {    qp_table_start_minus26[ i ] se(v)   num_points_in_qp_table_minus1[ i ] ue(v)    for( j = 0; j <=num_points_in_qp_table_minus1[ i ]; j++ ) {     delta_qp_in_val_minus1[i ][ j ] ue(v)     delta_qp_diff_val[ i ][ j ] ue(v)    }   }  } sps_sao_enabled_flag  u(1)  sps_alf_enabled_flag  u(1)  if(sps_alf_enabled_flag && ChromaArrayType != 0 )   sps_ccalf_enabled_flag u(1)  sps_transform_skip_enabled_flag  u(1)  if(sps_transform_skip_enabled_flag ) {  log2_transform_skip_max_size_minus2 ue(v)   sps_bdpcm_enabled_flag u(1)  }  sps_ref_wraparound_enabled_flag  u(1) sps_temporal_mvp_enabled_flag  u(1)  if( sps_temporal_mvp_enabled_flag)   sps_sbtmvp_enabled_flag  u(1)  sps_amvr_enabled_flag  u(1) sps_bdof_enabled_flag  u(1)  if( sps_bdof_enabled_flag )  sps_bdof_pic_present_flag  u(1)  sps_smvd_enabled_flag  u(1) sps_dmvr_enabled_flag  u(1)  if( sps_dmvr_enabled_flag)  sps_dmvr_pic_present_flag  u(1)  sps_mmvd_enabled_flag  u(1) sps_isp_enabled_flag  u(1)  sps_mrl_enabled_flag  u(1) sps_mip_enabled_flag  u(1)  if( ChromaArrayType != 0 )  sps_cclm_enabled_flag  u(1)  if( chroma_format_idc = = 1 ) {  sps_chroma_horizontal_collocated_flag  u(1)  sps_chroma_vertical_collocated_flag  u(1)  }  sps_mts_enabled_flag u(1)  if( sps_mts_enabled_flag) {   sps_explicit_mts_intra_enabled_flag u(1)   sps_explicit_mts_inter_enabled_flag  u(1)  } six_minus_max_num_merge_cand ue(v)  sps_sbt_enabled_flag  u(1) sps_affine_enabled_flag  u(1)  if( sps_affine_enabled_flag ) {  five_minus_max_num_subblock_merge_cand ue(v)   sps_affine_type_flag u(1)   if( sps_amvr_enabled_flag )    sps_affine_amvr_enabled_flag u(1)   sps_affine_prof_enabled_flag  u(1)   if(sps_affine_prof_enabled_flag )    sps_prof_pic_present_flag  u(1)  } sps_palette_enabled_flag  u(1)  if( ChromaArrayType = = 3 &&!sps_max_luma_transform_size_64_flag )   sps_act_enabled_flag  u(1)  if(sps_transform_skip_enabled_flag | | sps_palette_enabled_flag )  min_qp_prime_ts_minus4 ue(v)  sps_bcw_enabled_flag  u(1) sps_ibc_enabled_flag  u(1)  if( sps_ibc_enabled_flag )  six_minus_max_num_ibc_merge_cand ue(v)  sps_ciip_enabled_flag  u(1) if( sps_mmvd_enabled_flag )   sps_fpel_mmvd_enabled_flag  u(1)  if(MaxNumMergeC and >= 2 ) {   sps_gpm_enabled_flag  u(1)   if(sps_gpm_enabled_flag && MaxNumMergeCand >= 3 )   max_num_merge_cand_minus_max_num_gpm_cand ue(v)  } sps_lmcs_enabled_flag  u(1)  spsfinst_enabled_flag  u(1) sps_ladf_enabled_flag  u(1)  if( sps_ladf_enabled_flag ) {  sps_num_ladf_intervals_minus2  u(2)  sps_ladf_lowest_interval_qp_offset se(v)   for( i = 0; i <sps_num_ladf_intervals_minus2 + 1; i++ ) {    sps_ladf_qp_offset[ i ]se(v)    sps_ladf_delta_threshold_minus1[ i ] ue(v)   }  } log2_parallel_merge_level_minus2 ue(v) sps_explicit_scaling_list_enabled_flag  u(1) sps_dep_quant_enabled_flag  u(1)  if( !sps_dep_quant_enabled_flag )  sps_sign_data_hiding_enabled_flag  u(1) sps_virtual_boundaries_enabled_flag  u(1)  if(sps_virtual_boundaries_enabled_flag ) {  sps_virtual_boundaries_present_flag  u(1)   if(sps_virtual_boundaries_present_flag ) {   sps_num_ver_virtual_boundaries  u(2)    for( i = 0; i <sps_num_ver_virtual_boundaries; i++ )     sps_virtual_boundaries_pos_x[i ]   u(13)   sps_num_hor_virtual_boundaries  u(2)   for( i = 0; i <sps_num_hor_virtual_boundaries; i++ )    sps_virtual_boundaries_pos_y[ i]   u(13)   }  }  if( sps_ptl_dpb_hrd_params_present_flag ) {  sps_general_hrd_params_present_flag  u(1)   if(sps_general_hrd_params_present_flag ) {    general_hrd_parameters( )   if( sps_max_sublayers_minus1 > 0 )    sps_sublayer_cpb_params_present_flag  u(1)    firstSubLayer =sps_sublayer_cpb_params_present_flag ? 0 :     sps_max_sublayers_minus1   ols_hrd_parameters( firstSubLayer, sps_max_sublayers_minus1 )   }  } field_seq_flag  u(1)  vui_parameters_present_flag  u(1)  if(vui_parameters_present_flag )   vui_parameters( ) /* Specified in ITU-TH.SEI | ISO/IEC 23002-7 */  sps_extension_flag  u(1)  if(sps_extension_flag )   while( more_rbsp_data( ) )   sps_extension_data_flag  u(1)  rbsp_trailing_bits( ) }

An SPS table as above may be expanded as described above to incorporatea global motion present indicator as shown in Table 6:

sequence_parameter_set_rbsp( ) { Descriptor sps_sequence_parameter_set_id ue(v) . . . global_motion_present  u(1) rbsp_trailing_bits( ) }

Additional fields may be incorporated in an SPS to reflect furtherindicators as described in this disclosure.

In an embodiment, and still referring to FIG. 2, ansps_affine_enabled_flag in a PPS and/or SPS may specify whether affinemodel based motion compensation may be used for inter prediction. Ifsps_affine_enabled_flag is equal to 0, the syntax may be constrainedsuch that no affine model based motion compensation is used in the codelater video sequence (CLVS), and inter_affine_flag andcu_affine_type_flag may not be present in coding unit syntax of theCLVS. Otherwise (sps_affine_enabled_flag is equal to 1), affine modelbased motion compensation can be used in the CLVS.

Continuing to refer to FIG. 2, sps_affine_type_flag in a PPS and/or SPSmay specify whether 6-parameter affine model based motion compensationmay be used for inter prediction. If sps_affine_type_flag is equal to 0,syntax may be constrained such that no 6-parameter affine model basedmotion compensation is used in the CLVS, and cu_affine_type_flag may notpresent in coding unit syntax in the CLVS. Otherwise(sps_affine_type_flag equal to 1), 6-parameter affine model based motioncompensation may be used in CLVS. When not present, the value ofsps_affine_type_flag may be inferred to be equal to 0.

Still referring to FIG. 2, translational CPMVs may be signaled in thePPS. Control points may be predefined. For example, control point MV 0may be relative to a top left corner of a picture, MV 1 may be relativeto a top right corner, and MV 3 may be relative to a bottom left cornerof the picture. Table 4 illustrates an example approach for signalingCPMV data depending on a motion model used.

In an exemplary embodiment, and still referring to FIG. 2, an arrayamvr_precision_idx, which may be signaled in coding unit, coding tree,or the like, may specify a resolution AmvrShift of a motion vectordifference, which may be defined as a non-limiting example as shown inTable 7 as shown below. Array indices x0, y0 may specify the location(x0, y0) of a top-left luma sample of a considered coding block relativeto a top-left luma sample of the picture; whenamvr_precision_idx[x0][y0] is not present, it may be inferred to beequal to 0. Where an inter_affine_flag[x0][y0] is equal to 0, variablesMvdL0[x0][y0][0], MvdL0[x0][y0][1], MvdL1[x0][y0][0], MvdL1[x0][y0][1]representing modsion vector difference values corresponding to conseredblock, may be modified by shifting such values by AmvrShift, forinstance using MvdL0[x0][y0][0]=MvdL0[x0][y0][0]<<AmvrShift;MvdL0[x0][y0][1]=MvdL0[x0][y0][1]<<AmvrShift;MvdL1[x0][y0][0]=MvdL1[x0][y0][0]<<AmvrShift; andMvdL1[x0][y0][1]=MvdL1[x0][y0][1]<<AmvrShift. Whereinter_affine_flag[x0][y0] is equal to 1, variablesMvdCpL0[x0][y0][0][0], MvdCpL0[x0][y0][0][1], MvdCpL0[x0][y0][1][0],MvdCpL0[x0][y0][1][1], MvdCpL0[x0][y0][2][0] and MvdCpL0[x0][y0][2][1]may be modified via shifting, for instance as follows:MvdCpL0[x0][y0][0][0]=MvdCpL0[x0][y0][0][0]<<AmvrShift;MvdCpL1[x0][y0][0][1]=MvdCpL1[x0][y0][0][1]<<AmvrShift;MvdCpL0[x0][y0][1][0]=MvdCpL0[x0][y0][1][0]<<AmvrShift;MvdCpL1[x0][y0][1][1]=MvdCpL1[x0][y0][1][1]<<AmvrShift;MvdCpL0[x0][y0][2][0]=MvdCpL0[x0][y0][2][0]<<AmvrShift; andMvdCpL1[x0][y0][2][1]=MvdCpL1[x0][y0][2][1]<<AmvrShift

AmvrShift inter_affine_flag = =0 && inter_affine_flag CuPredMode[ chType][ x0 ] CuPredMode[ chType ][ x0 ] amvr_flag amvr_precision_id = =1 [ y0] = = MODE_IBC) [ y0 ] != MODE_IBC 0 — 2 (1/4 luma — 2 (1/4 luma sample)sample) 1 0 0 (1/16 luma 4 (1 luma sample) 3 (1/2 luma sample) sample) 11 4 (1 luma sample) 6 (4 luma samples) 4 (1 luma sample) 1 2 — — 6 (4luma samples)

With continued reference to FIG. 2, global motion may be relative to apreviously coded frame. When only one set of global motion parametersare present, motion may be relative to a frame that is presentedimmediately before a current frame.

Further referring to FIG. 2, global motion may represent a dominantmotion in a frame. Many blocks in a frame are likely to have a motionthat is same as very similar to a global motion. Exceptions may includeblocks with local motion. Keeping block motion compensation compatiblewith global motion may reduce encoder complexity and decoder complexityand improve compression efficiency.

In some implementations, and still referring to FIG. 2, if global motionis signaled in a header such as a PPS or a SPS, a motion model in theSPS may be applied to all blocks in a picture. For example, if globalmotion uses translational motion (e.g., motion model=0), all predictionunits (PUs) in a frame may also be limited to translational motion(e.g., motion model=0). In this case, adaptive motion models may not beused. This may also be signaled in an SPS using ause_gm_constrained_motion_models flag. When this flag is set to 1,adaptive motion models may not be used in a decoder, instead, a singlemotion model may be used for all PUs.

Still referring to FIG. 2, in some implementations of the currentsubject matter, motion signaling may not change over PUs. Instead, afixed motion model may be used by signaling a motion model once in SPS.Such an approach may replace global motion. Use of fixed motion modelmay be specified at an encoder to reduce complexity—for instance, theencoder may be limited to translational model—which can be advantageousfor low power devices, such as low computational power devices. Forexample, affine motion models may not be used; this may be specified,without limitation, in an encoder profile. Such an example may be usefulfor real-time applications, such as video conferencing, information ofthings (IoT) infrastructure, security cameras, and the like. By using afixed motion model, there may be no need to include excess signaling ina bitstream.

The current subject matter is not limited to coding techniques utilizingglobal motion but can apply to a broad range of coding techniques.

FIG. 3 is a process flow diagram illustrating an exemplary embodiment ofa process 300 of using a given motion model for all blocks in a picture.At step 305, a current block is received by a decoder. Current block maybe contained within a bitstream that a decoder receives. Bitstream mayinclude, for example, data found in a stream of bits that is an input toa decoder when using data compression. Bitstream may include informationnecessary to decode a video. Receiving bitstream may include extractingand/or parsing a block and associated signaling information from the bitstream. In some implementations, a current block may include a codingtree unit (CTU), a coding unit (CU), and/or a prediction unit (PU).

At step 310, and still referring to FIG. 2, a header associated with acurrent frame and including a signal characterizing that global motionis enabled, and further characterizing parameters of a motion model maybe extracted from bitstream. At step 315, a current frame may bedecoded. Decoding may include using parameters of motion model for eachcurrent block in current frame.

FIG. 4 is a system block diagram illustrating an exemplary decoder 400capable of decoding a bitstream 428 using a given motion model for allblocks in a picture. Decoder 400 may include an entropy decoderprocessor 404, an inverse quantization and inverse transformationprocessor 408, a deblocking filter 412, a frame buffer 416, motioncompensation processor 420 and/intra prediction processor 424.

In operation, and still referring to FIG. 4, bit stream 428 may bereceived by decoder 400 and input to entropy decoder processor 404,which may entropy decode portions of bit stream into quantizedcoefficients. Quantized coefficients may be provided to inversequantization and inverse transformation processor 408, which may performinverse quantization and inverse transformation to create a residualsignal, which may be added to an output of motion compensation processor420 or intra prediction processor 424 according to a processing mode.Output of motion compensation processor 420 and/or intra predictionprocessor 424 may include a block prediction based on a previouslydecoded block. A sum of block prediction and residual may be processedby deblocking filter 630 and stored in a frame buffer 640.

FIG. 5 is a process flow diagram illustrating an exemplary process 500of encoding a video using a given motion model for all blocks in apicture according to some aspects of the current subject matter that mayreduce encoding complexity while increasing compression efficiency. Atstep 505, a video frame may undergo initial block segmentation, whichmay be performed, as a non-limiting example, using a tree-structuredmacro block partitioning scheme that may include partitioning a pictureframe into CTUs and CUs.

At step 510, and still referring to FIG. 5, global motion for a currentblock may be determined. Determining may include determining a motionmodel for a global motion. At step 515, a block may be encoded andincluded in bitstream. Encoding may include utilizing inter predictionand intra prediction modes, for example. A flag in a header may be setto indicate that determined motion model (for the global motion) shouldbe used for all blocks during decoding.

FIG. 6 is a system block diagram illustrating an example video encoder600 capable of using a given global motion model for all blocks in apicture. Example video encoder 600 may receive an input video 604, whichmay be initially segmented and/or dividing according to a processingscheme, such as a tree-structured macro block partitioning scheme (e.g.,quad-tree plus binary tree). An example of a tree-structured macro blockpartitioning scheme may include partitioning a picture frame into largeblock elements called coding tree units (CTU). In some implementations,each CTU may be further partitioned one or more times into a number ofsub-blocks called coding units (CU). A final result of this portioningmay include a group of sub-blocks that may be called predictive units(PU). Transform units (TU) may also be utilized.

Still referring to FIG. 6, example video encoder 600 may include anintra prediction processor 415, a motion estimation/compensationprocessor 612 (also referred to as an inter prediction processor)capable of using a given motion model for all blocks in the picture, atransform /quantization processor 616, an inverse quantization/inversetransform processor 620, an in-loop filter 624, a decoded picture buffer628, and/or an entropy coding processor 632. Bit stream parameters maybe input to entropy coding processor 632 for inclusion in output bitstream 636.

In operation, and further referring to FIG. 2, for each block of a frameof an input video 604, whether to process the block via intra pictureprediction or using motion estimation/compensation may be determined.Block may be provided to intra prediction processor 608 or motionestimation/compensation processor 612. If block is to be processed viaintra prediction, intra prediction processor 608 may perform processingto output a predictor. If block is to be processed via motionestimation/compensation, motion estimation/compensation processor 612may perform processing including using a given motion model for allblocks in picture, if applicable.

Still referring to FIG. 6, a residual may be formed by subtractingpredictor from input video. Residual may be received bytransform/quantization processor 616, which may perform transformationprocessing (e.g., discrete cosine transform (DCT)) to producecoefficients, which may be quantized. Quantized coefficients and anyassociated signaling information may be provided to entropy codingprocessor 632 for entropy encoding and inclusion in output bit stream636. Entropy encoding processor 632 may support encoding of signalinginformation related to encoding a current block. In addition, quantizedcoefficients may be provided to inverse quantization/inversetransformation processor 620, which may reproduce pixels, which may becombined with a predictor and processed by in loop filter 624, an outputof which may be stored in decoded picture buffer 628 for use by motionestimation/compensation processor 612 that is capable of using a givenmotion model for all blocks in the picture.

With continued reference to FIG. 6, although a few variations have beendescribed in detail above, other modifications or additions arepossible. For example, in some implementations, current blocks mayinclude any symmetric blocks (8×8, 16×16, 32×32, 64×64, 128×128, and thelike) as well as any asymmetric block (8×4, 16×8, and the like).

Still referring to FIG. 6, in some implementations, a quadtree plusbinary decision tree (QTBT) may be implemented. In QTBT, at a CodingTree Unit level, partition parameters of QTBT may be dynamically derivedto adapt to local characteristics without transmitting any overhead.Subsequently, at a Coding Unit level, a joint-classifier decision treestructure may eliminate unnecessary iterations and control risk of falseprediction. In some implementations, LTR frame block update mode may beavailable as an additional option available at every leaf node of QTBT.

In some implementations, and continuing to refer to FIG. 6, additionalsyntax elements may be signaled at different hierarchy levels ofbitstream. For example, a flag may be enabled for an entire sequence byincluding an enable flag coded in a Sequence Parameter Set (SPS).Further, a CTU flag may be coded at the coding tree unit (CTU) level.

It is to be noted that any one or more of the aspects and embodimentsdescribed herein may be conveniently implemented using digitalelectronic circuitry, integrated circuitry, specially designedapplication specific integrated circuits (ASICs), field programmablegate arrays (FPGAs) computer hardware, firmware, software, and/orcombinations thereof, as realized and/or implemented in one or moremachines (e.g., one or more computing devices that are utilized as auser computing device for an electronic document, one or more serverdevices, such as a document server, etc.) programmed according to theteachings of the present specification, as will be apparent to those ofordinary skill in the computer art. These various aspects or featuresmay include implementation in one or more computer programs and/orsoftware that are executable and/or interpretable on a programmablesystem including at least one programmable processor, which may bespecial or general purpose, coupled to receive data and instructionsfrom, and to transmit data and instructions to, a storage system, atleast one input device, and at least one output device. Appropriatesoftware coding may readily be prepared by skilled programmers based onthe teachings of the present disclosure, as will be apparent to those ofordinary skill in the software art. Aspects and implementationsdiscussed above employing software and/or software modules may alsoinclude appropriate hardware for assisting in the implementation of themachine executable instructions of the software and/or software module.

Such software may be a computer program product that employs amachine-readable storage medium. A machine-readable storage medium maybe any medium that is capable of storing and/or encoding a sequence ofinstructions for execution by a machine (e.g., a computing device) andthat causes the machine to perform any one of the methodologies and/orembodiments described herein. Examples of a machine-readable storagemedium include, but are not limited to, a magnetic disk, an optical disc(e.g., CD, CD-R, DVD, DVD-R, etc.), a magneto-optical disk, a read-onlymemory “ROM” device, a random access memory “RAM” device, a magneticcard, an optical card, a solid-state memory device, an EPROM, an EEPROM,Programmable Logic Devices (PLDs), and/or any combinations thereof. Amachine-readable medium, as used herein, is intended to include a singlemedium as well as a collection of physically separate media, such as,for example, a collection of compact discs or one or more hard diskdrives in combination with a computer memory. As used herein, amachine-readable storage medium does not include transitory forms ofsignal transmission.

Such software may also include information (e.g., data) carried as adata signal on a data carrier, such as a carrier wave. For example,machine-executable information may be included as a data-carrying signalembodied in a data carrier in which the signal encodes a sequence ofinstruction, or portion thereof, for execution by a machine (e.g., acomputing device) and any related information (e.g., data structures anddata) that causes the machine to perform any one of the methodologiesand/or embodiments described herein.

Examples of a computing device include, but are not limited to, anelectronic book reading device, a computer workstation, a terminalcomputer, a server computer, a handheld device (e.g., a tablet computer,a smartphone, etc.), a web appliance, a network router, a networkswitch, a network bridge, any machine capable of executing a sequence ofinstructions that specify an action to be taken by that machine, and anycombinations thereof. In one example, a computing device may includeand/or be included in a kiosk.

FIG. 7 shows a diagrammatic representation of one embodiment of acomputing device in the exemplary form of a computer system 700 withinwhich a set of instructions for causing a control system to perform anyone or more of the aspects and/or methodologies of the presentdisclosure may be executed. It is also contemplated that multiplecomputing devices may be utilized to implement a specially configuredset of instructions for causing one or more of the devices to performany one or more of the aspects and/or methodologies of the presentdisclosure. Computer system 700 includes a processor 704 and a memory708 that communicate with each other, and with other components, via abus 712. Bus 712 may include any of several types of bus structuresincluding, but not limited to, a memory bus, a memory controller, aperipheral bus, a local bus, and any combinations thereof, using any ofa variety of bus architectures.

Memory 708 may include various components (e.g., machine-readable media)including, but not limited to, a random-access memory component, a readonly component, and any combinations thereof. In one example, a basicinput/output system 716 (BIOS), including basic routines that help totransfer information between elements within computer system 700, suchas during start-up, may be stored in memory 708. Memory 708 may alsoinclude (e.g., stored on one or more machine-readable media)instructions (e.g., software) 720 embodying any one or more of theaspects and/or methodologies of the present disclosure. In anotherexample, memory 708 may further include any number of program modulesincluding, but not limited to, an operating system, one or moreapplication programs, other program modules, program data, and anycombinations thereof.

Computer system 700 may also include a storage device 724. Examples of astorage device (e.g., storage device 724) include, but are not limitedto, a hard disk drive, a magnetic disk drive, an optical disc drive incombination with an optical medium, a solid-state memory device, and anycombinations thereof. Storage device 724 may be connected to bus 712 byan appropriate interface (not shown). Example interfaces include, butare not limited to, SCSI, advanced technology attachment (ATA), serialATA, universal serial bus (USB), IEEE 1394 (FIREWIRE), and anycombinations thereof. In one example, storage device 724 (or one or morecomponents thereof) may be removably interfaced with computer system 700(e.g., via an external port connector (not shown)). Particularly,storage device 724 and an associated machine-readable medium 728 mayprovide nonvolatile and/or volatile storage of machine-readableinstructions, data structures, program modules, and/or other data forcomputer system 700. In one example, software 720 may reside, completelyor partially, within machine-readable medium 728. In another example,software 720 may reside, completely or partially, within processor 704.

Computer system 700 may also include an input device 732. In oneexample, a user of computer system 700 may enter commands and/or otherinformation into computer system 700 via input device 732. Examples ofan input device 732 include, but are not limited to, an alpha-numericinput device (e.g., a keyboard), a pointing device, a joystick, agamepad, an audio input device (e.g., a microphone, a voice responsesystem, etc.), a cursor control device (e.g., a mouse), a touchpad, anoptical scanner, a video capture device (e.g., a still camera, a videocamera), a touchscreen, and any combinations thereof. Input device 732may be interfaced to bus 712 via any of a variety of interfaces (notshown) including, but not limited to, a serial interface, a parallelinterface, a game port, a USB interface, a FIREWIRE interface, a directinterface to bus 712, and any combinations thereof. Input device 732 mayinclude a touch screen interface that may be a part of or separate fromdisplay 736, discussed further below. Input device 732 may be utilizedas a user selection device for selecting one or more graphicalrepresentations in a graphical interface as described above.

A user may also input commands and/or other information to computersystem 700 via storage device 724 (e.g., a removable disk drive, a flashdrive, etc.) and/or network interface device 740. A network interfacedevice, such as network interface device 740, may be utilized forconnecting computer system 700 to one or more of a variety of networks,such as network 744, and one or more remote devices 748 connectedthereto. Examples of a network interface device include, but are notlimited to, a network interface card (e.g., a mobile network interfacecard, a LAN card), a modem, and any combination thereof. Examples of anetwork include, but are not limited to, a wide area network (e.g., theInternet, an enterprise network), a local area network (e.g., a networkassociated with an office, a building, a campus or other relativelysmall geographic space), a telephone network, a data network associatedwith a telephone/voice provider (e.g., a mobile communications providerdata and/or voice network), a direct connection between two computingdevices, and any combinations thereof. A network, such as network 744,may employ a wired and/or a wireless mode of communication. In general,any network topology may be used. Information (e.g., data, software 720,etc.) may be communicated to and/or from computer system 700 via networkinterface device 740.

Computer system 700 may further include a video display adapter 752 forcommunicating a displayable image to a display device, such as displaydevice 736. Examples of a display device include, but are not limitedto, a liquid crystal display (LCD), a cathode ray tube (CRT), a plasmadisplay, a light emitting diode (LED) display, and any combinationsthereof. Display adapter 752 and display device 736 may be utilized incombination with processor 704 to provide graphical representations ofaspects of the present disclosure. In addition to a display device,computer system 700 may include one or more other peripheral outputdevices including, but not limited to, an audio speaker, a printer, andany combinations thereof. Such peripheral output devices may beconnected to bus 712 via a peripheral interface 756. Examples of aperipheral interface include, but are not limited to, a serial port, aUSB connection, a FIREWIRE connection, a parallel connection, and anycombinations thereof.

The foregoing has been a detailed description of illustrativeembodiments of the invention. Various modifications and additions can bemade without departing from the spirit and scope of this invention.Features of each of the various embodiments described above may becombined with features of other described embodiments as appropriate inorder to provide a multiplicity of feature combinations in associatednew embodiments. Furthermore, while the foregoing describes a number ofseparate embodiments, what has been described herein is merelyillustrative of the application of the principles of the presentinvention. Additionally, although particular methods herein may beillustrated and/or described as being performed in a specific order, theordering is highly variable within ordinary skill to achieve embodimentsas disclosed herein. Accordingly, this description is meant to be takenonly by way of example, and not to otherwise limit the scope of thisinvention.

In the descriptions above and in the claims, phrases such as “at leastone of” or “one or more of” may occur followed by a conjunctive list ofelements or features. The term “and/or” may also occur in a list of twoor more elements or features. Unless otherwise implicitly or explicitlycontradicted by the context in which it is used, such a phrase isintended to mean any of the listed elements or features individually orany of the recited elements or features in combination with any of theother recited elements or features. For example, the phrases “at leastone of A and B;” “one or more of A and B;” and “A and/or B” are eachintended to mean “A alone, B alone, or A and B together.” A similarinterpretation is also intended for lists including three or more items.For example, the phrases “at least one of A, B, and C;” “one or more ofA, B, and C;” and “A, B, and/or C” are each intended to mean “A alone, Balone, C alone, A and B together, A and C together, B and C together, orA and B and C together.” In addition, use of the term “based on,” aboveand in the claims is intended to mean, “based at least in part on,” suchthat an unrecited feature or element is also permissible.

The subject matter described herein can be embodied in systems,apparatus, methods, and/or articles depending on the desiredconfiguration. The implementations set forth in the foregoingdescription do not represent all implementations consistent with thesubject matter described herein. Instead, they are merely some examplesconsistent with aspects related to the described subject matter.Although a few variations have been described in detail above, othermodifications or additions are possible. In particular, further featuresand/or variations can be provided in addition to those set forth herein.For example, the implementations described above can be directed tovarious combinations and sub-combinations of the disclosed featuresand/or combinations and sub-combinations of several further featuresdisclosed above. In addition, the logic flows depicted in theaccompanying figures and/or described herein do not necessarily requirethe particular order shown, or sequential order, to achieve desirableresults. Other implementations may be within the scope of the followingclaims.

What is claimed is:
 1. A decoder, the decoder configured to: receive abit stream including a current frame and a picture header associatedwith the entire current frame; determine, as a function of the pictureheader, that one global motion mode is enabled for the entire currentframe, the enabled global motion mode being selected from a groupincluding translational motion, 4-parameter affine motion, and6-parameter affine motion; detect, based on the enabled global motionmode, a plurality of parameters applicable to the entire frame, wherein:if the enabled global motion mode is translational motion: detecting theplurality of parameters further comprises detecting, in the pictureheader, a x direction translational motion vector component and a ydirection translational motion vector component; and the x directiontranslational motion vector component and the y direction translationalmotion vector component apply to the entire frame; if the enabled globalmotion mode is 4-parameter affine motion: detecting the plurality ofparameters further comprises detecting, in the picture header, fourexplicit affine motion parameters; and the four explicit affine motionparameters apply to the entire frame; and if the enabled global motionmode is 6-parameter affine motion: detecting the plurality of parametersfurther comprises detecting, in the picture header six explicit affinemotion parameters; and the six explicit affine motion parameters applyto the entire frame; and decode the current frame using the detectedparameters.
 2. The decoder of claim 1, wherein if the enabled globalmotion mode is translational motion, the decoder is further configuredto detect that affine global motion modes are disabled for the currentframe.
 3. The decoder of claim 1 wherein if the enabled global motionmode is 4-parameter affine motion and if coordinates of the currentframe are denoted x and y, x′ and y′ are coordinates of a referenceframe, and the four 4-parameter affine motion parameters are denoted a,b, c and f, then x′=ax+by +c and y′=−bx+ay+f.
 4. The decoder of claim 1wherein if the enabled global motion mode is 6-parameter affine motionand if coordinates of the current frame are denoted x and y, x′ and y′are coordinates of a reference frame, and the six 6-parameter affinemotion parameters are denoted a, b, c, d, e and f, then x′=ax+by +c andy′=dx+ey+f.
 5. A method, the method comprising: receiving, by a decoder,a bit stream including a current frame and a picture header associatedwith the entire current frame; determining, by the decoder and as afunction of the picture header, that one global motion mode is enabledfor the entire current frame, the enabled global motion mode beingselected from a group including translational motion, 4-parameter affinemotion, and 6-parameter affine motion; detecting, by the decoder andbased on the enabled global motion mode, a plurality of parametersapplicable to the entire frame, wherein: if the enabled global motionmode is translational motion: detecting the plurality of parametersfurther comprises detecting, in the picture header, a x directiontranslational motion vector component and a y direction translationalmotion vector component; and the x direction translational motion vectorcomponent and the y direction translational motion vector componentapply to the entire frame; if the enabled global motion mode is4-parameter affine motion: detecting the plurality of parameters furthercomprises detecting, in the picture header, four explicit affine motionparameters; and the four explicit affine motion parameters apply to theentire frame; and if the enabled global motion mode is 6-parameteraffine motion: detecting the plurality of parameters further comprisesdetecting, in the picture header six explicit affine motion parameters;and the six explicit affine motion parameters apply to the entire frame;and decoding, by the decoder, the current frame using the detectedparameters.
 6. The method of claim 5, wherein if the enabled globalmotion mode is translational motion, the decoder is further configuredto detect that affine global motion modes are disabled for the currentframe.
 7. The method of claim 5, wherein if the enabled global motionmode is 4-parameter affine motion and if coordinates of the currentframe are denoted x and y, x′ and y′ are coordinates of a referenceframe, and the four 4-parameter affine motion parameters are denoted a,b, c and f, then x′=ax+by +c and y′=−bx+ay+f.
 8. The method of claim 5wherein if the enabled global motion mode is 6-parameter affine motionand if coordinates of the current frame are denoted x and y, x′ and y′are coordinates of a reference frame, and the six 6-parameter affinemotion parameters are denoted a, b, c, d, e and f, then x′=ax+by +c andy′=dx+ey+f.